Conventionally, in electric brushes used in facial equipment, electric toothbrushes, electric razors, electric shoeshine machines, electric car-washing machines and the like, a movable part such as a brush head of facial equipment, a brush part of a toothbrush, a blade, a shoe polishing brush, and a car-washing brush reciprocates for aesthetic cares of skin, teeth, shaving and the like, and for polishing and washing of shoes and a car body. In addition, conventionally, in electric cutting machines such as electric saws and electric gravers, a movable part such as a blade of a saw and a blade of a graver reciprocates for processing such as cutting, shaving, and carving of wood, metal, and the like. Further, conventionally, in electric air pumps used in sphygmomanometers, a movable part of a diaphragm reciprocates for air intake and exhaust of the electric air pump.
As a structure for driving the movable part of electric brushes, electric cutting machines, and electric air pumps, a structure that converts the normal axial rotation of DC motor into linear reciprocation or rotational reciprocation with use of a motion direction conversion mechanism is often used. Such a structure in which a motion direction conversion mechanism is used requires the space for the complicated mechanism for converting the driving direction, and therefore cannot be easily downsized. In addition, the motion conversion mechanism generates significant noise at the time of driving, and causes power loss, and therefore the efficiency may be sacrificed. Under such circumstances, structures of actuators have been proposed in which a movable part is linearly reciprocated (see, for example, PTLS 1 to 3).
In PTL 1, a vibration-type linear actuator used in a reciprocation-type electric shaver and the like is disclosed. In this linear actuator, a movable member having a magnet disposed with its magnetization direction set to a lateral direction is disposed on an electromagnet of a stator, and the movable member (magnet) is reciprocated in the lateral direction with respect to the stator.
In addition, PTL 2 discloses a cylindrical linear drive actuator which can be mounted in cylindrical equipment such as a toothbrush. In this actuator, a plunger is provided on the outer periphery of a shaft serving as a moving object, and two ring-shaped magnets sandwiching a coil are inserted on the outer periphery of the plunger together with the coil. The coil is electrified to excite the plunger such that the plunger functions as an electromagnet, and thus the shaft is moved in the axis direction.
In addition, PTL 3 discloses a vibrator as a structure for linear reciprocation of a movable member. In this vibrator, a coil supported by a substrate is disposed to face a vibrating member which can vibrate in the axis direction of the coil. In the vibrating member, a magnet is disposed at the center of an annular spindle, and the magnet is supported by the spindle through a leaf spring disposed to surround the magnet such that the magnet can be moved in the axis direction of the coil.